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Science 101: Blood Chemistry and Your Dog

June 22, 2016 – The blood chemistry panel includes a number of tests a diagnostic laboratory runs on the non-cellular component of blood (serum) your veterinarian collects from your dog. These tests impart important information about organ function in your dog, providing clues to the cause of illness when he or she is sick, and helping to prevent future problems when he or she is well. When looking at your dog’s blood chemistry, your veterinarian may lump tests together based on the associated organ system. Many of the tests are not specific for only one organ system, so it is important that blood chemistry results are interpreted comprehensively and in the context of your dog’s clinical symptoms.

Total protein is the sum of the serum proteins albumin and globulins. Changes in total protein have different implications, depending on which component is altered.

Albumin is the most common protein present in serum. High levels of albumin may indicate dehydration while low levels may signal decreased liver function, intestinal disorders, blood loss or kidney disease.

Globulins are part of the immune system. They are elevated in the presence of inflammation or chronic infection. Decreases may be seen with blood loss, intestinal malfunction and immune deficiencies.

AST (aspartate aminotransferase) is an enzyme found in the liver, heart and muscle. When elevated, it can indicate damage to any of these organs.

ALT (alanine aminotransferase) is an enzyme made by the liver. Liver cell damage allows the enzyme to spill into the bloodstream, causing elevated serum levels. Low ALT levels are uncommon and may indicate liver failure, but interpretation is dependent on other chemistry abnormalities.

ALKP (alkaline phosphatase) is another liver enzyme, elevated with liver and/or metabolic disorders. It also is elevated during times of active bone growth; for this reason, it commonly is elevated in healthy young dogs.

GGT (gamma glutamyl transferase) is a liver enzyme that can be elevated in conditions of liver damage similar to those that affect ALKP.

Bilirubin is a pigment that results from the breakdown of red blood cells. Increases can be seen with liver or gallbladder malfunction, and anemia resulting from red blood cell destruction (hemolysis).

BUN (blood urea nitrogen) is a byproduct of normal protein metabolism, and the kidneys are responsible for filtering it from the blood. When this byproduct becomes too high in the blood, it is toxic. Reasons it may be elevated include improperly functioning kidneys, dehydration, heart disease and urinary obstruction.

Creatinine is a byproduct of normal muscle metabolism, and also is filtered by the kidneys. It can be elevated for the same reasons as BUN but is less affected by dehydration, so it is a more reliable indicator of decreased kidney function.

Phosphorus helps form bone and teeth. The kidneys maintain phosphorus at an optimal level, so elevation may indicate the kidneys are not functioning properly. Low phosphorus levels indicate increased loss, usually through the intestine.

Calcium has many functions in the body, including bone formation and regulating muscle contraction. It can be elevated for a number of reasons including kidney disease, certain types of cancer, and metabolic disturbances. Calcium and phosphorus are co-regulated and their relative values can be informative, particularly in the case of metabolic disorders.

Glucose is the sugar that powers the muscles and brain, and can change rapidly. Elevated blood glucose can indicate diabetes or acute stress, while decreased serum glucose can be due to liver, kidney or metabolic disorders.

Sodium (Na), potassium (K), and chloride (Cl) are collectively known as electrolytes. They have essential functions at the cellular level.

Na is increased in the case of dehydration. It is decreased in the presence of vomiting or diarrhea, kidney disease and some metabolic diseases.

K may be increased in the presence of dehydration, kidney disease and some metabolic diseases. Decreased K occurs in the presence of vomiting or diarrhea.

Na/K ratio is Na concentration divided by K. This is an important screening test for Addison’s disease. When this ratio is low, additional testing is needed.

Cl increases may indicate dehydration; decreases may be the result of vomiting or diarrhea.

Cholesterol is important in vitamin D metabolism, and in the formation of hormones and bile acids. Increases may be seen in the presence of metabolic diseases such as diabetes. Decreases may indicate liver or intestinal dysfunction.

Triglycerides are fat molecules in the blood stream. Elevations are common in the presence of metabolic diseases. Insufficient fasting prior to blood draw is the most common cause for elevated triglycerides.

Amylase and lipase are enzymes produced by the pancreas to aid in protein and fat digestion. They can be elevated when the pancreas is damaged. Other conditions that can lead to elevated amylase include kidney disease, treatment with certain types of medications, and gastrointestinal disease.

Total T4 measures thyroid function. Increases and decreases both indicate thyroid disease. A low functioning thyroid gland is most common in dogs. Total T4 is an inexpensive screening test, but additional testing and evaluation of clinical symptoms are needed to confirm a diagnosis of hypothyroidism.

These tests are an essential part of wellness screening and a first step toward diagnosing illness. Remember that all laboratory results are interpreted in the context of your dog’s clinical symptoms, so the good clinical judgment of your veterinarian is important. If you are concerned about your dog’s results, please talk to your veterinarian. Thank you to our laboratory partner, VCA Inc. (Antech Diagnostics,), for their support of the Golden Retriever Lifetime Study.